I've actually seen Werther's products with a may contain statement. Maybe those are more at risk.

For frosting I would think caramel sauce would work. The frosting might not be as thick or set up as hard.

Have not seen them in person, never new they existed until today, so I cannot speak for allergen safety.  But I just saw an ad for Werthers caramels for cooking.  They make a big point of being easy to unwrap, so it looks like they going after Kraft.

Striking out finding Kraft caramels this year.  We've used those in the past without problem. Brach's have a warning for everything under the sun. DH just called and said he found some Werther's soft caramels, but their website seems to have a CYA blanket statement..."While none of our products contain nuts and the utmost care is taken, we can not guarantee....."

I have a recipe for Apple cider cupcakes with salted caramel buttercream I was hoping to make today  The frosting calls for 1/2 bag Kraft caramels, melted.  Would caramel sauce work, do you think? Any suggestions?